This invention relates to devices and methods for the analysis of acoustic signals generated by the electrical contact in high energy power distribution equipment. In particular, this invention relates to a system and method for detecting the misalignment of electrical contacts in power line voltage regulators.
A power line voltage regulator is an electrical device which acts to effect changes in the voltage in an electrical power distribution system in response to changes in electrical load upon the power distribution system. Typically, these voltage regulators switch power at levels of approximately several hundred amperes and over ten thousand volts. These devices, however, do not change the voltage on the line in response to minor variations in the load. Because of the energy levels being switched by this device, the contacts used in the actual switching must be moved very rapidly and with a certain amount of precision. Because of these requirements, the devices typically do not have motor driven actuators for the electrical contacts but rather they are typically driven by a spring wound mechanism which takes approximately five seconds to wind. However, the actual switching occurs in approximately 0.03 seconds. From this fact, an appreciation of the time scale on which a typical voltage regulator operates may be gained. The presence of this motor driven spring wound mechanism is significant because it, it and of itself, produces acoustic signals which must be considered in any acoustic analysis of the device.
These voltage regulators are designed to work in the field for a period of between ten and twenty years before failure or replacement. Therefore, over the life of a typical device, a very large number of switching operations occur. Typically, the switching action in these devices occurs by means of two finger-like contacts or blades which slide off, one contacting shelf onto another contacting shelf. If these fingers are misaligned, either with respect to one another or with respect to the shelves, excessive wear and stress occurs on those structures which support the finger-like contacts. These voltage regulator units are typically sealed units in which the internal mechanism is contained in a special oil. Prior to the invention herein, the only way to detect misalignment of these contacts was to remove the unit from service and disassemble it for inspection. This in itself is not only costly but care must be taken upon reassembly to insure that all gases have been removed from the oil and the container holding the oil and the internal mechanism. Failure to replace a unit which has misaligned switching contacts (or blades) can result in a catastrophic failure of the unit in the field, thereby posing a threat to property and personnel who may be present in the switch yard where the voltage regulator is typically installed.
Thus, the basic problem exists of how to detect this misalignment without disassembly and without removal of the unit from service for longer than approximately 5 minutes.